I installed Konsta's LineageOS 16.0 for the RPi4. Then I installed GAPPS pico to get the Play Store, from where I installed Zoom.
I only had the RPF camera without a mic on my Pi, but I managed to setup a meeting with my laptop that had video and mic.
Initial impressions were quite good as I got video in both direction, and the audio from the laptop mic came through on the Pi's HDMI. Obviously I couldn't test the audio in the other direction.
The video and audio came through consistently from the laptop, but unfortunately, the video from the Pi occasionally froze on my first test. On my second meeting, the video worked throughout the meeting for over 10 mins, but then froze again when I started messing with the settings. so maybe if you just video and don't mess with the settings it will be fine
Screen sharing and whiteboard both seemed to work.
The video lag was under 1 second, and the audio was about half that, or less.